ISO 3966 INTERNATIONAL STANDARD. Measurement of fluid flow in closed conduits Velocity area method using Pitot static tubes

Transcription

1 INTERNATIONAL STANDARD ISO 3966 Second edition Measurement of fluid flow in closed conduits Velocity area method using Pitot static tubes Mesurage du débit des fluides dans les conduites fermées Méthode d'exploration du champ des vitesses au moyen de tubes de Pitot doubles Reference number ISO 3966:2008(E) ISO 2008

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3 Contents Page Foreword... iv 1 Scope Normative references Symbols and definitions Principle Design of Pitot tubes Requirements for use of Pitot tubes Positioning of Pitot tube Velocity computation Determination of the discharge velocity by graphical integration of the velocity area Determination of the discharge velocity by numerical integration of the velocity area Determination of the discharge velocity by arithmetical methods Corrections of local velocity measurements Errors Annex A (normative) Pitot tubes Annex B (normative) Correction to the measuring position of Pitot tubes used in a transverse velocity gradient Annex C (normative) Study concerning turbulence correction Annex D (normative) Damping of pressure gauges Annex E (normative) Measurements with a Pitot tube in a compressible fluid Annex F (normative) Determination of coefficient m for extrapolation near the wall Annex G (normative) Example of calculation of the uncertainty on the flow-rate measurement by means of Pitot tubes Bibliography ISO 2008 All rights reserved iii

4 Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 3966 was prepared by Technical Committee ISO/TC 30, Measurement of fluid flow in closed conduits, Subcommittee SC 5, Velocity and mass methods. This second edition results from the reinstatement of ISO 3966:1977 which was withdrawn in 2003 and with which it is technically identical. iv ISO 2008 All rights reserved

5 INTERNATIONAL STANDARD ISO 3966:2008(E) Measurement of fluid flow in closed conduits Velocity area method using Pitot static tubes 1 Scope This International Standard specifies a method for the determination in a closed conduit of the volume rate of flow of a regular flow: a) of a fluid of substantially constant density or corresponding to a Mach number not exceeding 0,25; b) with substantially uniform stagnation temperature across the measuring cross-section; c) running full in the conduit; d) under steady flow conditions. In particular, it deals with the technology and maintenance of Pitot static tubes, with the calculation of local velocities from measured differential pressures and with the computation of the flow rate by velocity integration. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 2186, Fluid flow in closed conduits Connections for pressure signal transmissions between primary and secondary elements ISO 7194, Measurement of fluid flow in closed conduits Velocity-area methods of flow measurement in swirling or asymmetric flow conditions in circular ducts by means of current-meters or Pitot static tubes ISO 2008 All rights reserved 1